1. Technical Field
This invention relates to a method of producing a coin-type electrochemical element which is used, for example, mounted on a surface and which has external lead terminal portions, and to a coin-type electrochemical element.
2. Background Art
As the coin-type electrochemical elements of this type, there have been known an electric double layer capacitor and a button cell. FIG. 4 is a perspective view illustrating, in a partly cut-away manner, the constitution of a conventional electric double layer capacitor. A pair of electric double layer electrodes 41a and 41b are arranged facing each other via insulating separator 44. Electric double layer electrode 41a has disk-like sheet or foil (hereinafter called sheet) 42a, and polarizing electrode 43a which is an activated carbon layer is formed for sheet 42a. Further, electric double layer electrode 41b has sheet 42b, and polarizing electrode 43b which is an activated carbon layer is formed for sheet 42b. 
Upper lid portion 46 of a metal container is formed on one main surface side of disk-like sheet 42a of a valve metal, and lower lid portion 45 of the metal container is separately formed on one main surface side of disk-like sheet 42b of the valve metal. A non-aqueous electrolyte which is not shown is filling electric double layer electrodes 41a, 41b and separator 44. Lower lid portion 45 and upper lid portion 46 are joined together so as to be closed via insulating ring packing 47 provided along the circumferential edges thereof.
FIG. 5A is a plan view of when an external lead terminal portion is connected to the electric double layer capacitor. FIG. 5B is a side view of when the external lead terminal portion is connected to the electric double layer capacitor.
FIGS. 5A and 5B are illustrating a state where external lead terminal portions 48 and 49 that have already been machined and cut into pieces are arranged by a parts feeder and are fed by a chuck onto the electric double layer capacitor, and are welded (not shown) to parts of lower lid portion 45 and upper lid portion 46.
FIGS. 6A, 6B and 6C are side views of when the external lead terminal is mounted on a printed board. FIG. 6A illustrates a state where the electric double layer capacitor is vertically placed. That is, both lower lid portion 45 and upper lid portion 46 are arranged at right angles with substrate 53.
External lead terminal portions 51 and 52 are connected to the outer surfaces of lower lid portion 45 and upper lid portion 46 of electric double layer capacitor 50. External lead terminal portions 51 and 52 are inserted in the holes formed in printed board 53, and the inserted portions are soldered to accomplish the mounting.
In FIG. 6B, the electric double layer capacitor is laid down. That is, both lower lid portion 45 and upper lid portion 46 are arranged in parallel with the printed board 58. External lead terminal portions 56 and 57 are connected to the outer surfaces of lower lid portion 45 and upper lid portion 46 of electric double layer capacitor 55. Namely, external lead terminal portions 56 and 57 are inserted in the holes formed in printed board 58, and the inserted portions are soldered to accomplish the mounting.
In FIG. 6C, the electric double layer capacitor 61 is laid down like in FIG. 6B. External lead terminal portions 62 and 63 are connected to the outer surfaces of lower lid portion 45 and upper lid portion 46. The difference of FIG. 6C from FIG. 6B is that the ends of external lead terminal portions 62 and 63 are arranged nearly in parallel with the connection land surface of printed board 64, and are mounted by soldering through a step of reflow.
In the foregoing was described an example of the electric double layer capacitor. In a button cell, too, electrodes having a separator between the positive electrode and the negative electrode are contained in the lower lid portion and in the upper lid portion of a two-abutted metal container, and the structure exhibits the appearance like that of the above electric double layer capacitor.
The electric double layer capacitors and button cells of the above structures have been disclosed in, for example, Japanese Patent Unexamined Publication No. 3-163813 and Japanese Patent Unexamined Publication No. 8-203497.
In the above coin-type electrochemical element, however, the anode (positive electrode) side is usually facing the cathode (negative electrode) side in the external lead terminal portion. If the external lead terminal portion of this constitution is used, however, the step becomes very cumbersome for welding the lower lid portion to the upper lid portion in the coin-type electrochemical element. Therefore, either external lead terminal portion must be cut into apiece so as to be fed, which is inconvenient.
In the coin-type electrochemical element of this constitution, further, deviation occurs in the positions of the external lead terminal portions welded to the lower lid portion and to the upper lid portion. In the case of small products, in particular, the external lead terminal portions are small, too, involving difficulty in supplying and positioning the coin-type electrochemical elements.
Besides, wide contact areas cannot be obtained between the conventional external lead terminal portions and the coin-type electrochemical element, and the welding strength may be weakened.